Re: widen vacuum buffer counters

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
Cc: Pg Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: widen vacuum buffer counters
Date: 2020-01-31 22:13:53
Message-ID: 4969.1580508833@sss.pgh.pa.us
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Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> writes:
> We recently noticed that vacuum buffer counters wraparound in extreme
> cases, with ridiculous results.

Ugh.

> I propose to backpatch this.

+1 for widening these counters, but since they're global variables, -0.2
or so for back-patching. I don't know of any reason that an extension
would be touching these, but I feel like the problem isn't severe enough
to justify taking an ABI-break risk.

Also, %zd is the wrong format code for int64. Recommended practice
these days is to use "%lld" with an explicit cast of the printf argument
to long long (just to be sure). That doesn't work safely before v12,
and if you did insist on back-patching further, you'd need to jump
through hoops to avoid having platform-specific format codes in a
translatable string. (The side-effects for translation seem like
an independent argument against back-patching.)

regards, tom lane

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